Needlestick prevention device

ABSTRACT

A needlestick prevention device for an injection device having a hollow needle comprises a sheath for attachment to the injection device. The sheath has three positions. In a first, inoperative position the sheath sealingly encloses the needle. In a second operative position a first part of the sheath is removed, a second part remains attached to the injection device and a third part is pivoted about a hinge to expose the needle. In a third, cover position the third part is pivoted about the hinge to cover at least the tip of the needle and is retained in position by a retaining device acting between the second part and the third part. The needlestick prevention device is simple to manufacture and use.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/171,795, filed Jul. 11, 2008, now pending, which claims the benefitof U.S. Provisional Patent Application No. 60/970,134, filed Sep. 5,2007, and claims priority to Great Britain Patent No. 0713580.9, filedJul. 12, 2007 and Great Britain Patent No. 0810753.4, filed Jun. 12,2008. The entire contents of each of the foregoing applications areincorporated herein by reference.

BACKGROUND

This invention relates to a needlestick prevention device for use withinjection devices, such as syringes.

A needlestick injury generally occurs in a medical environment, andparticularly before or after use of a syringe or other injection device,when the user accidentally sticks the needle into himself or herself, orindeed another person. It is of course important to prevent suchinjuries, since they can spread infections and diseases, as well asbeing painful and possibly incapacitating.

There are several known ways of trying to prevent needlestick injuries.For example, some syringes are made with needles which are retractedautomatically after use by means of a spring in the syringe. However,this requires a complex construction, and is expensive to manufacture.Further, it does not address the possibility of injury occurring beforethe injection is given.

Another known way is to replace the tubular sheath which is suppliedwith the syringe, protecting the needle. It is not now recommendedpractice to replace the sheath after the syringe has been used, becauseof the difficulty of placing the end of the needle accurately in thesheath. It is thought that trying to re-sheath the needle has actuallybeen the cause of a significant number of needlestick injuries. Further,the sheath can easily be removed again, so that injury is possible.

Yet another known needlestick prevention device is an automatic needlesheath mounted on the syringe barrel, the sheath being able to slide outto cover the needle. EP-A-0 268 445 shows a construction with astationary sheath part, and a movable sheath part spring-biassed to anextended position in which it covers the needle. The movable sheath partretracts to expose the needle for use, and when the retracting pressureis released the spring moves it automatically into its extendedposition, where it is locked. The movable sheath part has a projectionreceived in a track in the stationary part to determine its movement andto lock it. Again, this is a relatively complex construction which isexpensive to manufacture. A similar construction is found in WO03/105935.

SUMMARY OF THE INVENTION

According to the present invention, a needlestick prevention device foran injection device having a hollow needle comprises a sheath forattachment to the injection device, the sheath being so constructed andarranged that in a first, inoperative position it sealingly encloses theneedle, in a second, operative position a first part of the sheath isremoved, a second part remains attached to the injection device, and athird part is pivoted about a hinge means to expose the needle, and in athird, cover position the third part is pivoted about the hinge means tocover at least the tip of the needle, and is retained by the secondpart.

The device of the invention is simple to manufacture, as it only usesthe sheath, and no springs or tracks. It is also simple to use, butwithout the inherent danger of replacing the sheath over the needle, asthe pivotal movement effectively moves the sheath sideways over theneedle so that a user does not need to put their hands near the needle.In the cover position the third part is retained by the second part, sothat it is difficult to remove the third part again. The device istherefore simple to manufacture and use, and is safe in operation.

The second part is adapted for attachment to a hub which carries theneedle. It may be substantially cylindrical.

In the inoperative position the first and third parts extend axiallyfrom the second part beyond the end of the needle, to form asubstantially cylindrical cover for the needle. The first part mayextend round approximately one sixth to one half of the circumference ofthe cover. At its end remote from the second part, the first part has aprojection extending axially beyond the third part. The projection isgrasped in order to remove the first part.

The third part may be moved angularly from the inoperative position intothe operative position, and from the operative position into the coverposition by applying a force to the third part. The third part may havea tongue projecting beyond the tip of the needle in the inoperativeposition. The third part may be moved by applying a force to the tongue.

In the inoperative position the tip of the needle may be covered by thefirst part or the third part. The first part may have a projection, atits end remote from the second part, extending radially inwardly tocover the tip of the needle. Alternatively the third part may have aclosure member extending radially inwardly to cover the tip of theneedle.

The second and third parts are connected by the hinge means and aretaining means, which is engaged in the inoperative position and thecover position. The arrangement is such that in the inoperative positionthe first part prevents disengagement of the retaining means, but oncethe first part is removed the retaining means disengages on movement ofthe third part about the hinge means.

The hinge means may extend round one sixth to one quarter of thecircumference of the second part. It is preferably a spring or livinghinge, so that, on movement of the third part from the inoperativeposition and following disengagement of the retaining means, the hingemeans acts to move the third part automatically into the operativeposition. This automatic movement means that the user has to touch thethird part only once to move it into the operative position. In theoperative position the third part is conveniently as near as possible inline with the injection device, so that it has moved angularly through180°.

On movement of the third part from the operative position the hingemeans acts to move the third part towards the cover position once itsangular movement exceeds a predetermined amount. This amount may bebetween 80° and 100°. The hinge means may move the third part directlyinto the cover position, so that the user has to touch the third partonly once to effect this movement. Alternatively, a further manual forcemay be applied to move the third part into the cover position. In thecover position the third part moves beyond the inoperative position, andthe retaining means engages in a position where a permanent lockingarrangement is actuated.

In one embodiment the retaining means comprises at least one pair ofcorresponding stepped portions on the second and third parts. In theinoperative position the stepped portions of a pair are attached by aweakened portion which is adapted to break when the angular movement ofthe third part from the inoperative position exceeds a predeterminedamount. This amount may be between 30° and 45°. The hinge means mayextend between one sixth and one quarter of the circumference of thesecond part, with the weakened portion accounting for the remainingcircumference (approximately two thirds), after removal of the firstpart.

Preferably two pairs of stepped portions are provided on the second andthird parts, the pairs being separated by the hinge means, and thestepped portions of each pair being attached by a weakened portion. Thisensures that the weakened portions break easily, and that the hingemeans operates correctly.

In the cover position the stepped portion on the third part engagesbehind the stepped portion on the second part to retain the third partin the cover position. In the cover position the third part has movedbeyond the inoperative position, ensuring that it covers the needle, andis retained in that position, so that it is not easy to expose theneedle again.

In another embodiment, the retaining means may comprise at least one pegon one of the second or third parts engaging in a complementary slot onthe other part. Conveniently the or each peg is provided on the thirdpart, and the or each slot on the second part. The or each peg may havetwo detents, the first engaging in a recess in a slot in the inoperativeposition, and the second engaging in the recess in the cover position toprovide the permanent locking. There may be two pegs.

In a modification the retaining means may comprise a first mechanism forthe inoperative position and a second mechanism for the cover position.For the inoperative position, the first mechanism comprises a projectionon one of the second and third parts engaging in a complementary recesson the other part, and for the cover position the second mechanismcomprises a peg on one part engaging in a complementary slot on theother part. The projection and the peg may be on different parts. Thus,a projection on the third part may engage in a recess on the secondpart, and a peg on the second part may engage in a slot on the secondpart to provide the permanent locking. Conveniently there are twoprojections and two pegs.

A secondary locking mechanism may also be provided for the needle in thecover position. The secondary mechanism may comprise locking means onthe third part allowing the needle to pass through as the third partgoes beyond the inoperative position into the cover position, butpreventing the needle passing back again. The secondary lockingmechanism may comprise a pair of opposing hooks, arranged such that theneedle is able to pass between them in one direction, but not in theother.

In order to ensure that it is difficult to remove the whole sheath fromthe injection device, the sheath is attached to the hub carrying theneedle by a locking mechanism. The locking mechanism comprisesprojections on the sheath or the hub engaging in complementary recessesin the hub or the sheath. Alternatively, the sheath and hub may be madeas a single component, for example by injection moulding of plasticsmaterial.

The sheath may be moulded as a single component, with the first partsealing against the second and third parts, but not actually fused tothem. This is achieved by moulding a small gap around the first part. Asthe sheath cools it shrinks, but the second and third parts shrink morethan the first part, so that the gap disappears, and the first part isretained by the second and third parts. This means that the first part,being sealingly retained but not fused, can be readily removed, like atear-off strip, when the injection device is to be used. Alternatively,the second and third parts may be moulded as a single component, withthe first part being a strip, for example of foil, attachedsubsequently.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are illustrated, by way of exampleonly, in the accompanying drawings, in which:

FIG. 1 is a perspective view of a first needlestick prevention deviceattached to a hub carrying a needle of an injection device in aninoperative position;

FIG. 2 is a side view of the needlestick prevention device of FIG. 1with a first part removed;

FIG. 3 is a side view similar to FIG. 2, but showing an intermediateposition;

FIG. 4 is an enlarged perspective view of a portion of FIG. 3;

FIG. 5 is a section through part of the wall of the device;

FIG. 6 is a side view of the device in an operative position;

FIG. 7 is a side view of the device in a cover position;

FIG. 8 is a perspective view of a second needlestick prevention deviceattached to a hub carrying a needle of an injection device, in aninoperative position;

FIG. 9 is similar to FIG. 8, but shows the device in an operativeposition;

FIG. 10 is an enlarged perspective view of a portion of FIG. 9;

FIG. 11 is an enlarged perspective view of a further portion of FIG. 9;

FIG. 12 is similar to FIG. 8, but shows the device in a cover position.

FIG. 13 is a perspective view of a third needlestick prevention devicein an inoperative position;

FIG. 14 shows the device of FIG. 13 with a first part removed;

FIG. 15 is an enlarged perspective view of a portion of FIG. 14;

FIG. 16 is similar to FIG. 15, but in an operative position;

FIG. 17 shows the device of FIG. 13 in a cover position;

FIG. 18 is an enlarged view of a portion of FIG. 17;

FIG. 19 shows a further portion of FIG. 14;

FIG. 20 is a perspective view of a portion of a modified needlestickprevention device in an inoperative position; and

FIG. 21 is similar to FIG. 20, but with the device in a cover position.

DETAILED DESCRIPTION

The needlestick prevention device shown in FIGS. 1 to 7 comprises asheath 1 for attachment to an injection device, such as a syringe (notshown) with a hollow needle for injecting or removing fluid from a humanor animal body. The sheath 1 is shown attached to a hub 2 carrying theneedle 3 (see FIGS. 2 and 6). The hub 2 in turn is attached to a syringein any known way.

The sheath 1 is designed to prevent a user accidentally sticking theneedle into him or herself, or indeed another person, either before orafter correct use of the syringe. The sheath 1 is injection moulded ofplastics material such as polypropylene as a single component, formedfrom three parts 4,5,6.

The three parts 4,5,6 can take up three positions. The first,inoperative, position is shown in FIG. 1, where the three partssealingly enclose the needle 3. The second, operative, position is shownin FIG. 6, where the first part 4 is removed (see FIG. 2), the secondpart 5 remains attached to the hub 2, and the third part 6 is pivoted toexpose the needle 3. The third, cover, position is shown in FIG. 7,where the third part 6 is pivoted back again to cover the needle 3, andis retained by the second part 5.

The second part 5 is substantially cylindrical for attachment to the hub2 by projections (not shown) on the second part 5 received in recesses(not shown) on the hub 2. While this is a standard way of attaching asheath to a hub, in this case the projections and recesses are largerand deeper than in a standard attachment, to ensure that it is difficultto pull the sheath 1 off the hub 2. This means that the sheath 1 will beused correctly, and not as a standard sheath, which is normally pulledoff the hub to expose the needle for use.

The first part 4 and third part 6 extend axially from the distal end ofthe second part 5 to form a substantially cylindrical cover for theneedle 3. Both the first part 4 and third part 6 extend beyond theneedle tip. The first part 4 extends round approximately one sixth ofthe circumference of the second and third parts 5, 6 in the manner of atear-off strip. This is achieved in the moulding of the sheath 1, byproviding a small gap round the first part 4, which disappears as thesheath 1 cools and shrinks. The first part 4 extends axially beyond thethird part 6 at its distal end 8, which carries a radially-inwardlydirected projection 9 to seal off the distal end of the sheath 1. Thefirst part 4 is tapered inwardly slightly adjacent the second part 5.

The third part 6 extends round the remaining circumference of the secondpart 5 (about five-sixths of the circumference). The distal end 10 ofthe third part 6 is formed with a transverse notch 11, and an internallyribbed tongue 12 on the side of the notch 11 opposite the first part 4.The ribbed tongue 12 is slightly longer than the portions 13 adjacentthe first part 4. The projection 9 seals with the third part at the baseof the tongue 12. A reinforcing rib 14 extends from the base of thenotch 11 on opposing sides of the third part 6 to a point adjacent thesecond part 5.

The third part 6 is attached to the second part 5 by a retaining means19 and a hinge means 16. As best seen in FIGS. 2 to 4, the hinge 16 isopposite the first part 4, and extends between one-quarter and one-sixthof the circumference of the second part 5. The retaining means 19 is intwo parts 17,18 separated by the hinge 16. As best seen in FIGS. 4 and5, each retaining part 17, 18 comprises a radial stepped projection 20on the third part 6, and a corresponding radial stepped projection 21 onthe second part 5, each pair of corresponding radial projections 20,21being connected by a weakened portion 15. Each radial projection 20forms an external shoulder 22 on the third part 6. Each radialprojection 21 is substantially wedge-shaped, forming an externalabutment 23 and an internal shoulder 24 on the second part 5 (see FIG.5). The radial projections 20, 21 also add to the strength of theconstruction at the weakened portions 15. Each weakened portion 15extends from the projections 20, 21 towards the hinge 16, and has asplit line generally inclined to the axis of the sheath 1, and steppedaxially towards the hinge 16.

When the sheath 1 is moved from the inoperative position into theoperative position, as shown in FIGS. 2,3 and 5, movement of the thirdpart 6 towards the injection device firstly causes the weakened portions15 to break along the split lines. The third part 6 is then connected tothe second part 5 only by the hinge 16. This is constructed as a livinghinge, so that once the weakened portions 15 have broken, and the thirdpart 6 has moved through an angle of about 90°, the hinge 16automatically moves the third part 6 into the operative position shownin FIG. 6.

Similarly, when the sheath 1 is to be moved from the operative positionof FIG. 6 to the cover position of FIG. 7, the user performs the firstpart of the movement, but once the third part 6 has moved through anangle of about 90° the hinge 16 will move the third part 6 into thecover position of FIG. 7. It will be noted that in the cover positionthe third part 6 is over centre, so that it is in contact with the tipof the needle 3, to protect against needlestick. The third part 6 isretained in the cover position by the retaining means 19, with eachexternal shoulder 22 on the third part 6 engaging with the correspondinginternal shoulder 24 on the second part 5. It will be appreciated that,in order to achieve this, the second part 5 and third part 6 aredeflected relatively in a radial direction. Normally it will be thethird part 6 that is deflected radially inwardly, a movementaccommodated by the hinge 16. In the cover position the injection deviceis ready for disposal.

The sheath 1, as mentioned above, is injection moulded with two parts ina single moulding operation, resulting in a single component. The secondand third parts 5,6 are moulded as one part, and the first part 4 as aseparate part, with a small gap around it. The material shrinks as itcools after moulding, so that the gap disappears and the first part 4engages sealingly with the second and third parts 5,6, but without beingfused to them. Once cooled, the sheath 1 can be mounted on a hub 2carrying a needle 3, so that the needle 3 is sealingly enclosed.

For use, the hub 2 with the sheath 1 enclosing the needle 3 is attachedto an injection device such as a syringe. The sheath 1 is in theinoperative position of FIG. 1. The user then grasps the projection 9 atthe distal end of the first part 4, and pulls the first part to removeit from the second and third parts 5,6 (see FIG. 2). There is no dangerof the user touching the needle 3, as the projection 9 is located beyondthe end of the needle 3. The user discards the first part 4, and theneither grasps the tongue 12 or places it on the edge of a convenientsolid surface, and applies a force urging the third part 6 away from theneedle 3. As the third part moves the weakened portions 15 break, asshown in FIG. 3, leaving the third part 6 attached to the second part 5by the hinge 16. When the third part has moved through an angle of about90° the hinge 16 then urges it into the operative position of FIG. 6.The user then gives the injection, and when it is completed applies aforce to the free end 10 of the third part 6 to urge it towards theneedle 3 again. When the third part has moved through about 90° thehinge 16 urges it into the cover position of FIG. 7, with the shoulders22 on the third part 6 engaging with the internal shoulders 24 on thesecond part 5. In this position the third part 6 engages the needle tipand extends beyond it, protecting against the possibility ofneedlestick. It will be appreciated that there is no danger of aneedlestick injury in applying the force to urge the third part 6 intothe cover position, as the third part 6 in the operative position is notnear the needle tip. It will also be appreciated that the retainingmeans 19 ensure that the third part 6 cannot readily be moved away fromthe cover position to expose the needle 3 again.

A second embodiment is shown in FIGS. 8 to 12. This embodiment is amodification of the device of FIGS. 1 to 7, and corresponding referencenumerals have been applied to corresponding parts.

Thus, as shown in FIGS. 8 to 12, the sheath 1 is again formed from threeparts 4, 5, 6 attached to a hub 2 carrying a needle 3.

The second part 5 is substantially cylindrical and is attached to thehub 2, in this case by being integrally moulded. This means that thesheath 1 will be used correctly, and not as a standard sheath, which isnormally pulled off the hub to expose the needle for use.

The first part 4 and third part 6 extend axially from the distal end ofthe second part 5 to form a substantially cylindrical cover for theneedle 3. Both the first part 4 and third part 6 extend beyond theneedle tip. The first part 4 extends round approximately one quarter ofthe circumference of the second and third parts 5, 6 and is provided asa foil tear-off strip. The first part 4 extends axially beyond the thirdpart 6 at its distal end 8, forming a projection 9 which is grasped bythe user to remove the first part 4. At its proximal end the first part4 extends over the second part 5. Both the second part 5 and the thirdpart 6 have flat surfaces (see FIGS. 9 to 11) for attachment of thefirst part 4.

The third part 6 extends round the remaining circumference of the secondpart 5 (about three-quarters of the circumference). The distal end 10 ofthe third part 6 is formed with a closure member 29 to cover the tip ofthe needle 3.

The hub 2 with the needle 3, and the second and third parts 5, 6 areinjection moulded of plastics material as a single component. The foiltear-off strip (first part 4) is attached after moulding, in anysuitable way.

The third part 6 is attached to the second part 5 by a retaining means19 and a hinge means 16, which is a living hinge. As best seen in FIGS.9 and 10, the hinge 16 is opposite the first part 4, and extends betweenone-quarter and one-sixth of the circumference of the second part 5. Theretaining means 19 is opposite the hinge 16, and in the inoperativeposition is covered by the first part 4.

The retaining means 19 is best seen in FIGS. 9 and 10, and comprises apeg and slot arrangement. Two pegs 30 are provided on the proximal endof the third part 6, extending axially towards the second part 5, eachfor engagement in a complementary slot 31 formed in the second part 5.Each peg 30 is arranged adjacent a flat surface 32 of the third part 6,which is formed with a reinforcing rib 33 at the base of each peg 30. Anaxial slot 34 is formed in the third part 5 adjacent each peg 30, toprovide the necessary amount of radial resilience for each peg.

Each peg 30 has two detents 35, 36 projecting outwardly (away from eachother), and adapted to engage in a recess (not shown) in the respectiveslot 31. A first detent 35 is a retaining detent at the free end of thepeg 30. The retaining detent 35 has a rounded profile 37, so that it candisengage from the recess. In the inoperative position the first detent35 is engaged in the recess, from where it can be disengaged on movementof the third part 6 to the operative position. The second detent 36 isadjacent the base of the peg 30, and has a fir tree profile 38, with aninclined face 39 and a flat face 40, perpendicular to the axis of thethird part. The second detent 36 is a locking detent, which will notdisengage from the recess. The second detent 36 engages in the recesswhen the third part 6 moves into the cover position, to providepermanent locking.

The third part 6 also has a pair of inclined ledges 41 (only one ofwhich is shown). Each ledge 41 extends from the hinge 16 towards one ofthe pegs 30. The ledges 41 form a stop for the third part 6 when itmoves into the cover position, in order to define that position and toensure that the locking detents 36 on the pegs 30 engage in therecesses.

FIG. 11 shows a secondary locking mechanism 42 for the needle 3. Thesecondary locking mechanism comprises a pair of hooks 43 provided on theinternal surface of the third part 6. A gap 44 is defined between thefree ends of the hooks 43, the arrangement being such that the needle 3can deflect the hooks 43 resiliently to allow it to pass through the gap44. The hooks 43 then return to their original positions, in which theneedle 3 cannot pass back through the gap 44. This locks the needle 3into the third part in the cover position.

The cover position is shown in FIG. 12, with the third part 6 overcentre, the pegs 30 locked in the slots 31, and a proximal part 45 ofthe third part 6 between the ledge 41 and the free edge deformedoutwardly.

For use, the hub 2 with the sheath 1 enclosing the needle 3 is attachedto an injection device such as a syringe. The sheath 1 is in theinoperative position of FIG. 8 with the retaining detents 35 engaged inthe recesses. While the first part 4 is in position, the third part 6cannot move, as the first part 4 ensures it is connected to the secondpart 5. The user then grasps the projection 9 at the distal end of thefirst part 4, and pulls the first part to remove it from the second andthird parts 5, 6. There is no danger of the user touching the needle 3as the projection 9 is located beyond the end of the needle 3. Theremoval of the first part 4 enables the third part 6 to move relative tothe second part 5. The user discards the first part 4, and then graspsthe third part 6 and applies a force urging the third part 6 away fromthe needle 3. As the third part 6 moves the retaining detents 35disengage from the recesses, leaving the third part 6 attached to thesecond part 5 by the hinge 16. When the third part has moved through anangle of about 90° the hinge 16 then urges it into the operativeposition of FIG. 9. The user then gives the injection, and when it iscompleted applies a force to the free end of the third part 6 to urge ittowards the needle 3 again. There is no danger of a needlestick injuryin applying the force to urge the third part 6 into the cover position,as the third part 6 in the operative position is not near the needletip. When the third part has moved through about 90° the hinge 16 urgesit back towards the inoperative position. The user applies a furtherforce to move the third part 6 into the cover position of FIG. 12. Thereis no danger of the user touching the point of the needle 3, as in theinoperative position the point is protected by the closure member 29.The ledges 41 engage with the second part 5 to define the coverposition. This is about 8° over centre, and is sufficient to force thelocking detents 36 on the pegs 30 on the third part 6 into engagement inthe recesses on the second part 5. The needle 3 also passes through thegap 44 of the secondary locking mechanism. In the cover position thethird part 6 engages the needle tip and extends beyond it, protectingagainst the possibility of needlestick. It will be appreciated that thelocking detents 36 ensure that the third part 6 cannot readily be movedaway from the cover position to expose the needle 3 again.

A third embodiment is shown in FIGS. 13 to 19. This is a modification ofthe device shown in FIGS. 8 to 12, and corresponding reference numeralshave been applied to corresponding parts.

As with the embodiment of FIGS. 8 to 12, the sheath 1 is formed of threeparts 4, 5, 6, of which the second and third parts 5, 6 are mouldedintegrally with the hub 2 carrying the needle 3. The first part 4 is afoil tear-off strip. The hub 2 is shown attached to an injection device100.

In this embodiment the second part 5 has a rectangular external profile,and the third part 6 has a correspondingly-shaped base 50 for engagementwith the second part 5. Internally the second part 5 accommodates thehub 2 for the needle 3. The third part 6 has a substantially U-shapedportion 51 extending axially from three sides of the base 50 to form thecover for the needle 3, completed by the first part 4. The first andthird parts 4, 6 each extend beyond the needle tip, with the third part6 having a chamfered distal end 52. The first part 4 extends axiallybeyond the third part 6 at its distal end, forming a projection 9 whichis grasped by the user to remove the first part 4. At its proximal endthe first part 4 extends over the fourth, open side 53 of the base 50and the corresponding open side 54 of the second part 5. The second part5 and third part 6 each have flat surfaces, co-planar in the inoperativeposition, for attachment of the first part 4. The first part 4 isattached to the second and third parts in any suitable way.

The third part 6 is attached to the second part 5 by the retaining means19, and the hinge means 16, which as before is a living hinge. As bestseen in FIG. 16, the hinge 16 is provided on the side 55 of the base 50opposite the open side 53. The other two sides 56, 57 of the base 50extend over the corresponding sides 58, 59 of the second part 5, andtheir internal surfaces engage sealingly with the external surfaces ofthe second part 6.

The retaining means 19 is best seen in FIGS. 15 and 16, and comprises amodified peg and slot arrangement. Two pegs 30 again extend from thethird part 6 towards the second part 5, but are accommodated within thebase 50. As with the previous embodiment each peg has two detents 35,36, but these project towards the open side 53, rather than away fromeach other. The shape and function of the detents 35, 36 is otherwisethe same as that of the previous embodiment.

Each peg 30 has a complementary slot 31 formed externally on arespective side 58, 59 of the second part 5. In each slot 31 a recess 60is defined at the open distal end by a projection 61. The proximal baseend 62 of each slot 31 is closed, and extends below the projection 61 toaccommodate the peg 30 in the cover position. The base 62 of each slot31 forms a stop for the third part 6 when it moves into the coverposition, in order to define that position, in which the locking detent36 engages below the projection 61. This position is shown in FIGS. 17and 18. FIG. 14 shows the retaining means 19 in the inoperativeposition, in which the retaining detents 35 on the pegs 30 engagesealingly in the open ends of the slots 31. FIG. 15 shows the retainingmeans 19 with the pegs 30 just out of the slots 31, while FIG. 16 showsthe device in the operative position.

FIG. 19 shows the secondary locking mechanism 42, as the hooks 43provided on the third part 6, in a similar manner to FIG. 11.

In use, the embodiment of FIGS. 13 to 19 operates in a very similar wayto that of FIGS. 8 to 12. The only difference lies in the movement intothe cover position. As before, a force applied to the third part in theoperative position (FIG. 16) urges the third part 6 towards the needle 3again, and when the third part 6 has moved through about 90° the hinge16 urges it towards the inoperative position (FIG. 15). The user thenapplies a further force to move the third part 6 into the cover positionof FIGS. 17 and 18, where the point of the needle 3 is protected by theend 52 of the third part 6. The pegs 30 enter the slots 31, and themovement continues until the free ends of the pegs 30 engage the bases62 of the slots, in which position the locking detents 36 engage belowthe projections 61, to lock the third part 6 against movement away fromthe cover position in a direction to expose the needle 3 again. Theneedle 3 is also locked by the secondary locking mechanism 42.

FIGS. 20 and 21 show a modification of the embodiment of FIGS. 13 to 19.The modification is to the retaining means 19. In this embodiment theretaining means 19 has a first mechanism 63 for the inoperativeposition, and a second mechanism 64 for the cover position. The firstmechanism 63 comprises an externally projecting rib 65 of triangularprofile formed on each of the sides 58, 59 of the second part 5, andadapted to engage in a complementary recess 66 in the internal surfaceof each of the sides 56, 57 of the base 50. Each rib 63 extends onlypart of the way along the side 58 or 59. The engagement of the ribs 65in the recesses 66 will maintain the second and third parts 5, 6 inposition until the manual force is applied to the third part 6 move itinto the operative position.

The second mechanism 64 provides locking in the cover position, andcomprises a peg and slot arrangement. Two pegs 67 are provided on thethird part 6, extending axially towards the second part 5, andessentially parallel to the needle 3. Each peg 67 terminates in anoutward-facing hook 68. Each peg 67 is adapted to slide in an axial slot69 formed internally in the second part 5, adjacent the open side 54.Each slot 69 has an aperture 70 whose shape is complementary to the hook68 on the respective peg 67. The second part 5 also has stop ribs (notshown) extending internally on each side 58, 59 from the open side 54towards the hinge 16. On movement of the third part 6 into the coverposition each peg 67 moves axially into the second part 5. Each hook 68engages with a respective stop rib, which urges it resiliently towardsthe other hook 68 so that it is inclined to the needle 3. On furtheraxial movement each hook 68 moves past the stop rib and is returned byits resilience to its position parallel to the needle 3, and enters therespective aperture 70. The hooks 68 are then locked in the apertures70, since the stop ribs are constructed to prevent movement of the hooks68 in the reverse direction. The stop ribs thus provide a stop for thethird part 6 when it moves into the cover position, in order to definethat position and to ensure that the second mechanism 64 operates toprovide the locking.

For use, the hub 2 with the sheath 1 enclosing the needle 3 is attachedto an injection device such as a syringe 100. The sheath 1 is in theinoperative position of FIG. 20 with the retaining ribs 65 engaged inthe recesses 66. While the first part 4 is in position, the third part 6cannot move, as the first part 4 ensures it is connected to the secondpart 5. The user then grasps the projection 9 at the distal end of thefirst part 4, and pulls the first part to remove it from the second andthird parts 5, 6. There is no danger of the user touching the needle 3as the projection 9 is located beyond the end of the needle 3. Theremoval of the first part 4 enables the third part 6 to move relative tothe second part 5. The user discards the first part 4, and then graspsthe third part 6 and applies a force urging the third part 6 away fromthe needle 3. As the third part 6 moves the ribs 65 disengage from therecesses 66, leaving the third part 6 attached to the second part 5 bythe hinge 16. When the third part has moved through an angle of about90° the hinge 16 then urges it into the operative position. The userthen gives the injection, and when it is completed applies a force tothe free end of the third part 6 to urge it towards the needle 3 again.There is no danger of a needlestick injury in applying the force to urgethe third part 6 into the cover position, as the third part 6 in theoperative position is not near the needle tip. When the third part hasmoved through about 90° the hinge 16 urges it back towards theinoperative position. The user applies a further force to move the thirdpart 6 into the cover position of FIG. 21. There is no danger of theuser touching the point of the needle 3, as in the inoperative positionthe point is protected by the end 52 of the third part 6. The ribs 65move into and then out of the recesses 66, and then the hooks 68 moveover the stop ribs, being deflected resiliently by them, and then engagein the locking apertures 70, to define the cover position. This is about8° over centre. The needle 3 also passes through the gap 44 of thesecondary locking mechanism. In the cover position the third part 6engages the needle tip and extends beyond it, protecting against thepossibility of needlestick. It will be appreciated that the lockingmechanism 64 ensures that the third part 6 cannot readily be moved awayfrom the cover position to expose the needle 3 again.

In all the embodiments the sheath 1 thus provides a needlestickprevention device which is simple to manufacture and to use.

The invention claimed is:
 1. A needlestick prevention device for aninjection device having a hollow needle comprises a sheath forattachment to said injection device, said sheath having first, secondand third parts, and being so constructed and arranged that in a first,inoperative position said sheath sealingly encloses said needle, in asecond, operative position said first part of the sheath is removed,said second part remains attached to said injection device, and saidthird part is pivoted about a hinge to expose said needle, and in athird, cover position said third part is pivoted about said hinge tocover at least the tip of said needle and is retained by said secondpart, wherein said second and third parts are connected by said hingeand a retaining portion, said retaining portion being engaged in saidinoperative position and said cover position, said retaining portioncomprises at least one peg on one of said second or third parts engagingin a complementary slot on the other of said second or third parts,wherein each peg has first and second detents, said first detentengaging in a recess in a respective said slot in said inoperativeposition, and said second detent engaging in said same recess in saidrespective slot in said cover position.
 2. A needlestick preventiondevice as claimed in claim 1, wherein said second part is adapted forattachment to a hub which carries said needle.
 3. A needlestickprevention device as claimed in claim 1, wherein in said inoperativeposition said first and third parts extend axially from said second partbeyond the end of said needle, to form a substantially cylindrical coverfor said needle.
 4. A needlestick prevention device as claimed in claim1, wherein at its end remote from said second part, said first part hasa projection extending axially beyond said third part.
 5. A needlestickprevention device as claimed in claim 1, wherein said third part ismovable angularly from said inoperative position into said operativeposition, and from said operative position into said cover position byapplying a force to said third part.
 6. A needlestick prevention deviceas claimed in claim 1, wherein said second and third parts are connectedby said hinge means and a retaining means, said retaining means beingengaged in said inoperative position and said cover position.
 7. Aneedlestick prevention device as claimed in claim 6, wherein said hingemeans is constructed such that, on movement of said third part from saidinoperative position and following disengagement of said retainingmeans, said hinge means acts to move said third part automatically intosaid operative position.
 8. A needlestick prevention device as claimedin claim 1, wherein on movement of said third part from said operativeposition said hinge means acts to move said third part towards saidcover position once its angular movement exceeds a predetermined amount.9. A needlestick prevention device as claimed in claim 6, wherein insaid cover position said third part is beyond said inoperative position,and said retaining means engages in a position where a permanent lockingarrangement is actuated.
 10. A needlestick prevention device as claimedin claim 1, wherein the or each said peg is provided on said third part,and the or each said slot on said second part.
 11. A needlestickprevention device as claimed in claim 1, wherein a secondary lockingmechanism is provided for said needle in said cover position.